The manufacture of steel by the basic oxygen process, commonly referred to as the BOP or BOF process, is well known and widely used in the art. However, one problem with the conventional basic oxygen process when production of low alloy steel having a low carbon content is desired is the increasing quantity of oxygen that reacts with the metal rather than with the carbon as the carbon content decreases. Metallic oxidation results in loss to the slag of valuable elements such as iron and manganese. Such metallic oxidation is also costly because oxygen is consumed in excess of the steel making requirements. Furthermore, oxidation of other metallic alloying materials may result in a deterioration in the quality of the steel and necessitate costly and time consuming post-decarburization procedures. Excess metallic oxidation will also increase the temperature of the melt and the oxide content of the slag both of which are detrimental to the refractory lining of the refining vessel. All of these problems reduce the efficiency of the BOF process.
The problems described above are exacerbated when steel having an ultra low carbon content, i.e., 0.02 weight percent or less, is desired.
Recently, there have been reported processes for the production of ultra low carbon steel by use of a top blowing process in combination with some form of oxygen and/or inert gas injection from beneath the melt surface. This may be undesirable because retrofit of a top-blowing BOF facility to be compatible with a bottom blowing processes is very costly.
Accordingly it is an object of this invention to provide an improved basic oxygen process for the production of low alloy steel.
It is another object of this invention to provide an improved basic oxygen process for the production of low alloy steel having an ultra low carbon content.
It is a further object of this invention to provide an improved basic oxygen process for the production of ultra low carbon low alloy steel while reducing the amount of iron and other metals oxidized into the slag thus improving the yield of the process and resulting in a more efficient process.
It is still another object of this invention to provide an improved basic oxygen process for the production of ultra low carbon low alloy steel while reducing the high melt temperatures normally associated with the making of these steels by the conventional basic oxygen process.
It is still another object of this invention to provide an improved basic oxygen process for the production of ultra low carbon low alloy steel while avoiding the need to also inject oxygen or other gases into the melt from below the melt surface.